Light recycling for additive manufacturing optimization

ABSTRACT

A method and an apparatus pertaining to recycling and reuse of unwanted light in additive manufacturing can multiplex multiple beams of light including at least one or more beams of light from one or more light sources. The multiple beams of light may be reshaped and blended to provide a first beam of light. A spatial polarization pattern may be applied on the first beam of light to provide a second beam of light. Polarization states of the second beam of light may be split to reflect a third beam of light, which may be reshaped into a fourth beam of light. The fourth beam of light may be introduced as one of the multiple beams of light to result in a fifth beam of light.

CROSS REFERENCE TO RELATED PATENT APPLICATION

The present disclosure is part of a non-provisional patent applicationclaiming the priority benefit of

U.S. Patent Application No. 62/248,758, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,765, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,770, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,776, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,783, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,791, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,799, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,966, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,968, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,969, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,980, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,989, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,780, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,787, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,795, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,821, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,829, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,833, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,835, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,839, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,841, filed on Oct. 30, 2015,

U.S. Patent Application No. 62/248,847, filed on Oct. 30, 2015, and

U.S. Patent Application No. 62/248,848, filed on Oct. 30, 2015, whichare incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure generally relates to optics and, morespecifically, to an optical system that recycles rejected light inadditive manufacturing applications.

BACKGROUND

In laser-based additive manufacturing systems, a mask is applied topattern the light. The applied pattern enables the light to be splitinto negative and positive images, one used to build parts and the otherpotentially discarded. Liquid crystal based light valves allow for thespatial modulation of transmitted or reflected light by rotating theelectromagnetic wave polarization state. A typical example would havepolarized light “drive beam” passing through a liquid crystal filledlight valve which then spatially imprints a pattern in polarizationspace on the drive beam. The polarization state of the light desired isallowed to continue to the rest of the optical system, and the unwantedstate is rejected and thrown away to a beam dump or other energyrejection device.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present disclosureare described with reference to the following figures, wherein likereference numerals refer to like parts throughout the various figuresunless otherwise specified.

FIG. 1A illustrates an additive manufacturing system;

FIG. 1B is a top view of a structure being formed on an additivemanufacturing system;

FIG. 2 illustrates an additive manufacturing method;

FIG. 3A is a cartoon illustrating an additive manufacturing systemincluding lasers;

FIG. 3B is a detailed description of the light patterning unit shown inFIG. 3A;

FIG. 3C is one embodiment of an additive manufacturing system with a“switchyard” for directing and repatterning light using multiple imagerelays;

FIG. 3D illustrates a simple mirror image pixel remapping;

FIG. 3E illustrates a series of image transforming image relays forpixel remapping; and

FIG. 3F illustrates an patternable electron energy beam additivemanufacturing system;

FIG. 3G illustrates a detailed description of the electron beampatterning unit shown in FIG. 3F

FIG. 4 is a diagram of a layout of an example apparatus for laser lightrecycling in an additive manufacturing process in accordance with anembodiment of the present disclosure.

FIG. 5 is a diagram depicting the percent of maximum power delivered forvarious pattern fill factors in accordance with an embodiment of thepresent disclosure.

FIG. 6 is a diagram depicting the increase in intensity for variouspattern fill factors in accordance with an embodiment of the presentdisclosure.

FIG. 7 is a flowchart of an example process in accordance with thepresent disclosure.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings that form a part thereof, and in which is shown by way ofillustrating specific exemplary embodiments in which the disclosure maybe practiced. These embodiments are described in sufficient detail toenable those skilled in the art to practice the concepts disclosedherein, and it is to be understood that modifications to the variousdisclosed embodiments may be made, and other embodiments may beutilized, without departing from the scope of the present disclosure.The following detailed description is, therefore, not to be taken in alimiting sense.

The present disclosure proposes an optical system suitable for reducingthe light wasted in the additive manufacturing system as caused byrejection of unwanted light due to the pattern to be printed. Theproposed optical system may be utilized in, for example and not limitedto, laser-based additive manufacturing techniques where a mask isapplied to the light. Advantageously, in various embodiments inaccordance with the present disclosure, the thrown-away energy may berecycled and used to maintain high throughput rates. Moreover, thethrown-away energy may be recycled and reused to increase intensity toprint more difficult materials.

By recycling and re-use rejected light, system intensity can beincreased proportional to the fraction of light rejected. This allowsfor all the energy to be used to maintain high printing rates.Additionally, the recycling of the light potentially enables a “bar”print where a single bar sweeps across the build platform.

An additive manufacturing system is disclosed which has one or moreenergy sources, including in one embodiment, one or more laser orelectron beams, positioned to emit one or more energy beams. Beamshaping optics may receive the one or more energy beams from the energysource and form a single beam. An energy patterning unit receives orgenerates the single beam and transfers a two-dimensional pattern to thebeam, and may reject the unused energy not in the pattern. An imagerelay receives the two-dimensional patterned beam and focuses it as atwo-dimensional image to a desired location on a height fixed or movablebuild platform (e.g. a powder bed). In certain embodiments, some or allof any rejected energy from the energy patterning unit is reused.

In some embodiments, multiple beams from the laser array(s) are combinedusing a beam homogenizer. This combined beam can be directed at anenergy patterning unit that includes either a transmissive or reflectivepixel addressable light valve. In one embodiment, the pixel addressablelight valve includes both a liquid crystal module having a polarizingelement and a light projection unit providing a two-dimensional inputpattern. The two-dimensional image focused by the image relay can besequentially directed toward multiple locations on a powder bed to builda 3D structure.

As seen in FIG. 1, an additive manufacturing system 100 has an energypatterning system 110 with an energy source 112 that can direct one ormore continuous or intermittent energy beam(s) toward beam shapingoptics 114. After shaping, if necessary, the beam is patterned by anenergy patterning unit 116, with generally some energy being directed toa rejected energy handling unit 118. Patterned energy is relayed byimage relay 120 toward an article processing unit 140, typically as atwo-dimensional image 122 focused near a bed 146. The bed 146 (withoptional walls 148) can form a chamber containing material 144 dispensedby material dispenser 142. Patterned energy, directed by the image relay120, can melt, fuse, sinter, amalgamate, change crystal structure,influence stress patterns, or otherwise chemically or physically modifythe dispensed material 144 to form structures with desired properties.

Energy source 112 generates photon (light), electron, ion, or othersuitable energy beams or fluxes capable of being directed, shaped, andpatterned. Multiple energy sources can be used in combination. Theenergy source 112 can include lasers, incandescent light, concentratedsolar, other light sources, electron beams, or ion beams. Possible lasertypes include, but are not limited to: Gas Lasers, Chemical Lasers, DyeLasers, Metal Vapor Lasers, Solid State Lasers (e.g. fiber),Semiconductor (e.g. diode) Lasers, Free electron laser, Gas dynamiclaser, “Nickel-like” Samarium laser, Raman laser, or Nuclear pumpedlaser.

A Gas Laser can include lasers such as a Helium-neon laser, Argon laser,Krypton laser, Xenon ion laser, Nitrogen laser, Carbon dioxide laser,Carbon monoxide laser or Excimer laser.

A Chemical laser can include lasers such as a Hydrogen fluoride laser,Deuterium fluoride laser, COIL (Chemical oxygen-iodine laser), or Agil(All gas-phase iodine laser).

A Metal Vapor Laser can include lasers such as a Helium-cadmium (HeCd)metal-vapor laser, Helium-mercury (HeHg) metal-vapor laser,Helium-selenium (HeSe) metal-vapor laser, Helium-silver (HeAg)metal-vapor laser, Strontium Vapor Laser, Neon-copper (NeCu) metal-vaporlaser, Copper vapor laser, Gold vapor laser, or Manganese (Mn/MnCl₂)vapor laser.

A Solid State Laser can include lasers such as a Ruby laser, Nd:YAGlaser, NdCrYAG laser, Er:YAG laser, Neodymium YLF (Nd:YLF) solid-statelaser, Neodymium doped Yttrium orthovanadate (Nd:YVO₄) laser, Neodymiumdoped yttrium calcium oxoborateNd:YCa₄O(BO₃)³ or simply Nd:YCOB,Neodymium glass (Nd:Glass) laser, Titanium sapphire (Ti:sapphire) laser,Thulium YAG (Tm:YAG) laser, Ytterbium YAG (Yb:YAG) laser, Ytterbium:2O₃(glass or ceramics) laser, Ytterbium doped glass laser (rod, plate/chip,and fiber), Holmium YAG (Ho:YAG) laser, Chromium ZnSe (Cr:ZnSe) laser,Cerium doped lithium strontium (or calcium)aluminum fluoride (Ce:LiSAF,Ce:LiCAF), Promethium 147 doped phosphate glass (147Pm⁺³:Glass)solid-state laser, Chromium doped chrysoberyl (alexandrite) laser,Erbium doped anderbium-ytterbium co-doped glass lasers, Trivalenturanium doped calcium fluoride (U:CaF₂) solid-state laser, Divalentsamarium doped calcium fluoride (Sm:CaF₂) laser, or F-Center laser.

A Semiconductor Laser can include laser medium types such as GaN, InGaN,AlGaInP, AlGaAs, InGaAsP, GaInP, InGaAs, InGaAsO, GaInAsSb, lead salt,Vertical cavity surface emitting laser (VCSEL), Quantum cascade laser,Hybrid silicon laser, or combinations thereof.

For example, in one embodiment a single Nd:YAG q-switched laser can beused in conjunction with multiple semiconductor lasers. In anotherembodiment, an electron beam can be used in conjunction with anultraviolet semiconductor laser array. In still other embodiments, atwo-dimensional array of lasers can be used. In some embodiments withmultiple energy sources, pre-patterning of an energy beam can be done byselectively activating and deactivating energy sources.

Beam shaping unit 114 can include a great variety of imaging optics tocombine, focus, diverge, reflect, refract, homogenize, adjust intensity,adjust frequency, or otherwise shape and direct one or more energy beamsreceived from the energy source 112 toward the energy patterning unit116. In one embodiment, multiple light beams, each having a distinctlight wavelength, can be combined using wavelength selective mirrors(e.g. dichroics) or diffractive elements. In other embodiments, multiplebeams can be homogenized or combined using multifaceted mirrors,microlenses, and refractive or diffractive optical elements.

Energy patterning unit 116 can include static or dynamic energypatterning elements. For example, photon, electron, or ion beams can beblocked by masks with fixed or movable elements. To increase flexibilityand ease of image patterning, pixel addressable masking, imagegeneration, or transmission can be used. In some embodiments, the energypatterning unit includes addressable light valves, alone or inconjunction with other patterning mechanisms to provide patterning. Thelight valves can be transmissive, reflective, or use a combination oftransmissive and reflective elements. Patterns can be dynamicallymodified using electrical or optical addressing. In one embodiment, atransmissive optically addressed light valve acts to rotate polarizationof light passing through the valve, with optically addressed pixelsforming patterns defined by a light projection source. In anotherembodiment, a reflective optically addressed light valve includes awrite beam for modifying polarization of a read beam. In yet anotherembodiment, an electron patterning device receives an address patternfrom an electrical or photon stimulation source and generates apatterned emission of electrons.

Rejected energy handling unit 118 is used to disperse, redirect, orutilize energy not patterned and passed through the energy pattern imagerelay 120. In one embodiment, the rejected energy handling unit 118 caninclude passive or active cooling elements that remove heat from theenergy patterning unit 116. In other embodiments, the rejected energyhandling unit can include a “beam dump” to absorb and convert to heatany beam energy not used in defining the energy pattern. In still otherembodiments, rejected beam energy can be recycled using beam shapingoptics 114. Alternatively, or in addition, rejected beam energy can bedirected to the article processing unit 140 for heating or furtherpatterning. In certain embodiments, rejected beam energy can be directedto additional energy patterning systems or article processing units.

Image relay 120 receives a patterned image (typically two-dimensional)from the energy patterning unit 116 and guides it toward the articleprocessing unit 140. In a manner similar to beam shaping optics 114, theimage relay 120 can include optics to combine, focus, diverge, reflect,refract, adjust intensity, adjust frequency, or otherwise shape anddirect the patterned image.

Article processing unit 140 can include a walled chamber 148 and bed144, and a material dispenser 142 for distributing material. Thematerial dispenser 142 can distribute, remove, mix, provide gradationsor changes in material type or particle size, or adjust layer thicknessof material. The material can include metal, ceramic, glass, polymericpowders, other melt-able material capable of undergoing a thermallyinduced phase change from solid to liquid and back again, orcombinations thereof. The material can further include composites ofmelt-able material and non-melt-able material where either or bothcomponents can be selectively targeted by the imaging relay system tomelt the component that is melt-able, while either leaving along thenon-melt-able material or causing it to undergo avaporizing/destroying/combusting or otherwise destructive process. Incertain embodiments, slurries, sprays, coatings, wires, strips, orsheets of materials can be used. Unwanted material can be removed fordisposable or recycling by use of blowers, vacuum systems, sweeping,vibrating, shaking, tipping, or inversion of the bed 146.

In addition to material handling components, the article processing unit140 can include components for holding and supporting 3D structures,mechanisms for heating or cooling the chamber, auxiliary or supportingoptics, and sensors and control mechanisms for monitoring or adjustingmaterial or environmental conditions. The article processing unit can,in whole or in part, support a vacuum or inert gas atmosphere to reduceunwanted chemical interactions as well as to mitigate the risks of fireor explosion (especially with reactive metals).

Control processor 150 can be connected to control any components ofadditive manufacturing system 100. The control processor 150 can beconnected to variety of sensors, actuators, heating or cooling systems,monitors, and controllers to coordinate operation. A wide range ofsensors, including imagers, light intensity monitors, thermal, pressure,or gas sensors can be used to provide information used in control ormonitoring. The control processor can be a single central controller, oralternatively, can include one or more independent control systems. Thecontroller processor 150 is provided with an interface to allow input ofmanufacturing instructions. Use of a wide range of sensors allowsvarious feedback control mechanisms that improve quality, manufacturingthroughput, and energy efficiency.

FIG. 1B is a cartoon illustrating a bed 146 that supports material 144.Using a series of sequentially applied, two-dimensional patterned energybeam images (squares in dotted outline 124), a structure 149 isadditively manufactured. As will be understood, image patterns havingnon-square boundaries can be used, overlapping or interpenetratingimages can be used, and images can be provided by two or more energypatterning systems. In other embodiments, images can be formed inconjunction with directed electron or ion beams, or with printed orselective spray systems.

FIG. 2 is a flow chart illustrating one embodiment of an additivemanufacturing process supported by the described optical and mechanicalcomponents. In step 202, material is positioned in a bed, chamber, orother suitable support. The material can be a powder capable of beingmelted, fused, sintered, induced to change crystal structure, havestress patterns influenced, or otherwise chemically or physicallymodified to form structures with desired properties.

In step 204, unpatterned energy is emitted by one or more energyemitters, including but not limited to solid state or semiconductorlasers, or electrical power supply flowing electrons down a wire. Instep 206, the unpatterned energy is shaped and modified (e.g. intensitymodulated or focused). In step 208, this unpatterned energy ispatterned, with energy not forming a part of the pattern being handledin step 210 (this can include conversion to waste heat, or recycling aspatterned or unpatterned energy). In step 212, the patterned energy, nowforming a two-dimensional image is relayed toward the material. In step214, the image is applied to the material, building a portion of a 3Dstructure. These steps can be repeated (loop 218) until the image (ordifferent and subsequent image) has been applied to all necessaryregions of a top layer of the material. When application of energy tothe top layer of the material is finished, a new layer can be applied(loop 216) to continue building the 3D structure. These process loopsare continued until the 3D structure is complete, when remaining excessmaterial can be removed or recycled.

FIG. 3A is one embodiment of an additive manufacturing system 300 thatuses multiple semiconductor lasers as part of an energy patterningsystem 310. A control processor 350 can be connected to variety ofsensors, actuators, heating or cooling systems, monitors, andcontrollers to coordinate operation of multiple lasers 312, lightpatterning unit 316, and image relay 320, as well as any other componentof system 300. These connections are generally indicated by a dottedoutline 351 surrounding components of system 300. As will beappreciated, connections can be wired or wireless, continuous orintermittent, and include capability for feedback (for example, thermalheating can be adjusted in response to sensed temperature). The multiplelasers 312 can emit a beam 301 of light at a 1000 nm wavelength that,for example, is 90 mm wide by 20 mm tall. The beam 301 is resized byimaging optics 370 to create beam 303. Beam 303 is 6 mm wide by 6 mmtall, and is incident on light homogenization device 372 which blendslight together to create blended beam 305. Beam 305 is then incident onimaging assembly 374 which reshapes the light into beam 307 and is thenincident on hot cold mirror 376. The mirror 376 allows 1000 nm light topass, but reflects 450 nm light. A light projector 378 capable ofprojecting low power light at 1080p pixel resolution and 450 nm emitsbeam 309, which is then incident on hot cold mirror 376. Beams 307 and309 overlay in beam 311, and both are imaged onto optically addressedlight valve 380 in a 20 mm wide, 20 mm tall image. Images formed fromthe homogenizer 372 and the projector 378 are recreated and overlaid onlight valve 380.

The optically addressed light valve 380 is stimulated by the light(typically ranging from 400-500 nm) and imprints a polarization rotationpattern in transmitted beam 313 which is incident upon polarizer 382.The polarizer 382 splits the two polarization states, transmittingp-polarization into beam 317 and reflecting s-polarization into beam 315which is then sent to a beam dump 318 that handles the rejected energy.As will be understood, in other embodiments the polarization could bereversed, with s-polarization formed into beam 317 and reflectingp-polarization into beam 315. Beam 317 enters the final imaging assembly320 which includes optics 384 that resize the patterned light. This beamreflects off of a movable mirror 386 to beam 319, which terminates in afocused image applied to material bed 344 in an article processing unit340. The depth of field in the image selected to span multiple layers,providing optimum focus in the range of a few layers of error or offset.

The bed 390 can be raised or lowered (vertically indexed) within chamberwalls 388 that contain material 344 dispensed by material dispenser 342.In certain embodiments, the bed 390 can remain fixed, and optics of thefinal imaging assembly 320 can be vertically raised or lowered. Materialdistribution is provided by a sweeper mechanism 392 that can evenlyspread powder held in hopper 394, being able to provide new layers ofmaterial as needed. An image 6 mm wide by 6 mm tall can be sequentiallydirected by the movable mirror 386 at different positions of the bed.

When using a powdered ceramic or metal material in this additivemanufacturing system 300, the powder can be spread in a thin layer,approximately 1-3 particles thick, on top of a base substrate (andsubsequent layers) as the part is built. When the powder is melted,sintered, or fused by a patterned beam 319, it bonds to the underlyinglayer, creating a solid structure. The patterned beam 319 can beoperated in a pulsed fashion at 40 Hz, moving to the subsequent 6 mm×6mm image locations at intervals of 10 ms to 0.5 ms (with 3 to 0.1 msbeing desirable) until the selected patterned areas of powder have beenmelted. The bed 390 then lowers itself by a thickness corresponding toone layer, and the sweeper mechanism 392 spreads a new layer of powderedmaterial. This process is repeated until the 2D layers have built up thedesired 3D structure. In certain embodiments, the article processingunit 340 can have a controlled atmosphere. This allows reactivematerials to be manufactured in an inert gas, or vacuum environmentwithout the risk of oxidation or chemical reaction, or fire or explosion(if reactive metals are used).

FIG. 3B illustrates in more detail operation of the light patterningunit 316 of FIG. 3A. As seen in FIG. 3B, a representative input pattern333 (here seen as the numeral “9”) is defined in an 8×12 pixel array oflight projected as beam 309 toward mirror 376. Each grey pixelrepresents a light filled pixel, while white pixels are unlit. Inpractice, each pixel can have varying levels of light, includinglight-free, partial light intensity, or maximal light intensity.Unpatterned light 331 that forms beam 307 is directed and passes througha hot/cold mirror 376, where it combines with patterned beam 309. Afterreflection by the hot/cold mirror 376, the patterned light beam 311formed from overlay of beams 307 and 309 in beam 311, and both areimaged onto optically addressed light valve 380. The optically addressedlight valve 380, which would rotate the polarization state ofunpatterned light 331, is stimulated by the patterned light beam 309,311 to selectively not rotate the polarization state of polarized light307, 311 in the pattern of the numeral “9” into beam 313. The unrotatedlight representative of pattern 333 in beam 313 is then allowed to passthrough polarizer mirror 382 resulting in beam 317 and pattern 335.Polarized light in a second rotated state is rejected by polarizermirror 382, into beam 315 carrying the negative pixel pattern 337consisting of a light-free numeral “9”.

Other types of light valves can be substituted or used in combinationwith the described light valve. Reflective light valves, or light valvesbase on selective diffraction or refraction can also be used. In certainembodiments, non-optically addressed light valves can be used. These caninclude but are not limited to electrically addressable pixel elements,movable mirror or micro-mirror systems, piezo or micro-actuated opticalsystems, fixed or movable masks, or shields, or any other conventionalsystem able to provide high intensity light patterning. For electronbeam patterning, these valves may selectively emit electrons based on anaddress location, thus imbuing a pattern on the beam of electronsleaving the valve.

FIG. 3C is one embodiment of an additive manufacturing system thatincludes a switchyard system enabling reuse of patterned two-dimensionalenergy. Similar to the embodiment discussed with respect to FIG. 1A, anadditive manufacturing system 220 has an energy patterning system withan energy source 112 that directs one or more continuous or intermittentenergy beam(s) toward beam shaping optics 114. After shaping, the beamis two-dimensionally patterned by an energy patterning unit 230, withgenerally some energy being directed to a rejected energy handling unit222. Patterned energy is relayed by one of multiple image relays 232toward one or more article processing units 234A, 234B, 234C, or 234D,typically as a two-dimensional image focused near a movable or fixedheight bed. The bed (with optional walls) can form a chamber containingmaterial dispensed by material dispenser. Patterned energy, directed bythe image relays 232, can melt, fuse, sinter, amalgamate, change crystalstructure, influence stress patterns, or otherwise chemically orphysically modify the dispensed material to form structures with desiredproperties.

In this embodiment, the rejected energy handling unit has multiplecomponents to permit reuse of rejected patterned energy. Relays 228A,228B, and 22C can respectively transfer energy to an electricitygenerator 224, a heat/cool thermal management system 225, or an energydump 226. Optionally, relay 228C can direct patterned energy into theimage relay 232 for further processing. In other embodiments, patternedenergy can be directed by relay 228C, to relay 228B and 228A forinsertion into the energy beam(s) provided by energy source 112. Reuseof patterned images is also possible using image relay 232. Images canbe redirected, inverted, mirrored, sub-patterned, or otherwisetransformed for distribution to one or more article processing units.234A-D. Advantageously, reuse of the patterned light can improve energyefficiency of the additive manufacturing process, and in some casesimprove energy intensity directed at a bed, or reduce manufacture time.

FIG. 3D is a cartoon 235 illustrating a simple geometricaltransformation of a rejected energy beam for reuse. An input pattern 236is directed into an image relay 237D capable of providing a mirror imagepixel pattern 238. As will be appreciated, more complex pixeltransformations are possible, including geometrical transformations, orpattern remapping of individual pixels and groups of pixels. Instead ofbeing wasted in a beam dump, this remapped pattern can be directed to anarticle processing unit to improve manufacturing throughput or beamintensity.

FIG. 3E is a cartoon 235 illustrating multiple transformations of arejected energy beam for reuse. An input pattern 236 is directed into aseries of image relays 237B-E capable of providing a pixel pattern 238.

FIGS. 3F and 3G illustrates a non-light based energy beam system 240that includes a patterned electron beam 241 capable of producing, forexample, a “P” shaped pixel image. A high voltage electricity powersystem 243 is connected to an optically addressable patterned cathodeunit 245. In response to application of a two-dimensional patternedimage by projector 244, the cathode unit 245 is stimulated to emitelectrons wherever the patterned image is optically addressed. Focusingof the electron beam pattern is provided by an image relay system 247that includes imaging coils 246A and 246B. Final positioning of thepatterned image is provided by a deflection coil 248 that is able tomove the patterned image to a desired position on a bed of additivemanufacturing component 249.

In another embodiment supporting light recycling and reuse, multiplexmultiple beams of light from one or more light sources are provided. Themultiple beams of light may be reshaped and blended to provide a firstbeam of light. A spatial polarization pattern may be applied on thefirst beam of light to provide a second beam of light. Polarizationstates of the second beam of light may be split to reflect a third beamof light, which may be reshaped into a fourth beam of light. The fourthbeam of light may be introduced as one of the multiple beams of light toresult in a fifth beam of light. In effect, this or similar systems canreduce energy costs associated with an additive manufacturing system. Bycollecting, beam combining, homogenizing and re-introducing unwantedlight rejected by a spatial polarization valve or light valve operatingin polarization modification mode, overall transmitted light power canpotentially be unaffected by the pattern applied by a light valve. Thisadvantageously results in an effective re-distribution of the lightpassing through the light valve into the desired pattern, increasing thelight intensity proportional to the amount of area patterned.

Combining beams from multiple lasers into a single beam is one way toincreasing beam intensity. In one embodiment, multiple light beams, eachhaving a distinct light wavelength, can be combined using eitherwavelength selective mirrors or diffractive elements. In certainembodiments, reflective optical elements that are not sensitive towavelength dependent refractive effects can be used to guide amultiwavelength beam.

Patterned light can be directed using movable mirrors, prisms,diffractive optical elements, or solid state optical systems that do notrequire substantial physical movement. In one embodiment, amagnification ratio and an image distance associated with an intensityand a pixel size of an incident light on a location of a top surface ofa powder bed can be determined for an additively manufactured,three-dimensional (3D) print job. One of a plurality of lens assembliescan be configured to provide the incident light having the magnificationratio, with the lens assemblies both a first set of optical lenses and asecond sets of optical lenses, and with the second sets of opticallenses being swappable from the lens assemblies. Rotations of one ormore sets of mirrors mounted on compensating gantries and a final mirrormounted on a build platform gantry can be used to direct the incidentlight from a precursor mirror onto the location of the top surface ofthe powder bed. Translational movements of compensating gantries and thebuild platform gantry are also able to ensure that distance of theincident light from the precursor mirror to the location of the topsurface of the powder bed is substantially equivalent to the imagedistance. In effect, this enables a quick change in the optical beamdelivery size and intensity across locations of a build area fordifferent powdered materials while ensuring high availability of thesystem.

In certain embodiments, a plurality of build chambers, each having abuild platform to hold a powder bed, can be used in conjunction withmultiple optical-mechanical assemblies arranged to receive and directthe one or more incident energy beams into the build chambers. Multiplechambers allow for concurrent printing of one or more print jobs insideone or more build chambers. In other embodiments, a removable chambersidewall can simplify removal of printed objects from build chambers,allowing quick exchanges of powdered materials. The chamber can also beequipped with an adjustable process temperature controls.

In another embodiment, one or more build chambers can have a buildchamber that is maintained at a fixed height, while optics arevertically movable. A distance between final optics of a lens assemblyand a top surface of powder bed a may be managed to be essentiallyconstant by indexing final optics upwards, by a distance equivalent to athickness of a powder layer, while keeping the build platform at a fixedheight. Advantageously, as compared to a vertically moving the buildplatform, large and heavy objects can be more easily manufactured, sinceprecise micron scale movements of the build platform are not needed.Typically, build chambers intended for metal powders with a volume morethan ˜0.1-0.2 cubic meters (i.e., greater than 100-200 liters or heavierthan 500-1,000 kg) will most benefit from keeping the build platform ata fixed height.

In one embodiment, a portion of the layer of the powder bed may beselectively melted or fused to form one or more temporary walls out ofthe fused portion of the layer of the powder bed to contain anotherportion of the layer of the powder bed on the build platform. Inselected embodiments, a fluid passageway can be formed in the one ormore first walls to enable improved thermal management.

Improved powder handling can be another aspect of an improved additivemanufacturing system. A build platform supporting a powder bed can becapable of tilting, inverting, and shaking to separate the powder bedsubstantially from the build platform in a hopper. The powdered materialforming the powder bed may be collected in a hopper for reuse in laterprint jobs. The powder collecting process may be automated, andvacuuming or gas jet systems also used to aid powder dislodgement andremoval

Some embodiments of the disclosed additive manufacturing system can beconfigured to easily handle parts longer than an available chamber. Acontinuous (long) part can be sequentially advanced in a longitudinaldirection from a first zone to a second zone. In the first zone,selected granules of a granular material can be amalgamated. In thesecond zone, unamalgamated granules of the granular material can beremoved. The first portion of the continuous part can be advanced fromthe second zone to a third zone, while a last portion of the continuouspart is formed within the first zone and the first portion is maintainedin the same position in the lateral and transverse directions that thefirst portion occupied within the first zone and the second zone. Ineffect, additive manufacture and clean-up (e.g., separation and/orreclamation of unused or unamalgamated granular material) may beperformed in parallel (i.e., at the same time) at different locations orzones on a part conveyor, with no need to stop for removal of granularmaterial and/or parts.

In another embodiment, additive manufacturing capability can be improvedby use of an enclosure restricting an exchange of gaseous matter betweenan interior of the enclosure and an exterior of the enclosure. Anairlock provides an interface between the interior and the exterior;with the interior having multiple additive manufacturing chambers,including those supporting power bed fusion. A gas management systemmaintains gaseous oxygen within the interior at or below a limitingoxygen concentration, increasing flexibility in types of powder andprocessing that can be used in the system.

In another manufacturing embodiment, capability can be improved byhaving a 3D printer contained within an enclosure, the printer able tocreate a part having a weight greater than or equal to 2,000 kilograms.A gas management system may maintain gaseous oxygen within the enclosureat concentrations below the atmospheric level. In some embodiments, awheeled vehicle may transport the part from inside the enclosure,through an airlock, since the airlock operates to buffer between agaseous environment within the enclosure and a gaseous environmentoutside the enclosure, and to a location exterior to both the enclosureand the airlock.

Other manufacturing embodiments involve collecting powder samples inreal-time in a powder bed fusion additive manufacturing system. Aningester system is used for in-process collection and characterizationsof powder samples. The collection may be performed periodically and theresults of characterizations result in adjustments to the powder bedfusion process. The ingester system can optionally be used for one ormore of audit, process adjustments or actions such as modifying printerparameters or verifying proper use of licensed powder materials.

Yet another improvement to an additive manufacturing process can beprovided by use of a manipulator device such as a crane, lifting gantry,robot arm, or similar that allows for the manipulation of parts thatwould be difficult or impossible for a human to move is described. Themanipulator device can grasp various permanent or temporary additivelymanufactured manipulation points on a part to enable repositioning ormaneuvering of the part.

According to the present disclosure, an optical system capable ofrecycling rejected, unwanted and/or unused light is provided. Recyclingand re-using unwanted light may increase the intensity of laser emittedlight that is provided to a build platform. Moreover, recycling andre-using unwanted light may reduce energy costs associated with thesystem. By collecting, beam combining, homogenizing and re-introducingunwanted light rejected by a spatial polarization valve or light valveoperating in polarization modification mode, overall transmitted lightpower can potentially be unaffected by the pattern applied by the lightvalve. This advantageously results in an effective re-distribution ofthe light passing through the light valve into the desired pattern,thereby increasing the light intensity proportional to the amount ofarea patterned. This has particular use with regards to advancedadditive manufacturing methods using powder bed fusion techniques (suchas those described herein with respect to FIGS. 1A-3B) and in particularwith laser additive manufacturing. This is because increased intensitycan allow for shorter dwell times and faster print rates to increasematerial conversion rate while maintaining efficiency.

By way of a light valve or light modulator, a spatial pattern of lightcan be imprinted on a beam of light. When optical intensity is of aconcern or figure of merit of the optical system, conservation of systempower is a priority. Liquid crystal based devices are capable ofpatterning a polarized beam by selectively rotating “pixels” in the beamand then passing the beam through a polarizer to separate the rotatedand non-rotated pixels. Instead of dumping the rejected polarizationstate, the photons may be combined and homogenized with the originalinput beam(s) to the light valve. The optical path may be divided intothree segments, including: 1) optical transmission fraction betweenlight source(s) and light valve (denoted as “f₁” herein), 2) opticaltransmission fraction between light valve and source, e.g., accountingfor the return loop (denoted as “f₂” herein), and fraction of the lightvalve that is patterned for the desired transmission state (denoted as“f_(p)” herein). The final light power may be expressed as follows inEquation 1:

$P = {P_{0}\frac{\left( {f_{1}f_{p}} \right)}{1 - {f_{1}{f_{2}\left( {1 - f_{p}} \right)}}}}$

Thus, according to Equation 1, as the transmission fractions f₁ and f₂are increased to a full value of 1, the final power equals the initialpower regardless of fraction of the beam that is patterned. The finalintensity is increased relative to the initial intensity proportional tothe amount of area patterned. This increased intensity requirescompensation in the dwell time, however this is known a priori.

One example implementation of this concept is in the field of additivemanufacturing where lasers are used to melt a powdered layer ofmaterial. Without beam recycling, as the patterned area fill factordecreases, the material print rate also decreases, thereby lowering theoverall mass production rate of the printer. Compensation in dwell timedue to recycling of the light is such that for higher intensities, thedwell time is shortened in a non-linear fashion. Shorter dwell timestend to result in ever faster print rates and faster overall massconversion rates. This ability to increase the rate of material printingfor low fill factor print areas enables an additive manufacturingmachine to maintain high levels of powder to engineered shape conversionrates, hence resulting in a higher performance product.

A further example implementation of this concept is in the use of a barof light which sweeps over the build platform and is modulated on andoff as swept to create a two-dimensional (2D) solid layer from thepowder substrate. The use of recycled light in conjunction with thisexample is novel. The use of a bar, swept over the entire buildplatform, requires that it needs to be capable of always printing at100% fill factor. Typically, however, only 10-33% of the build platformis ever used. This low fill factor means that, on average, the capitalequipment in laser power is 3 to 10 times oversized for the system. If,however, the light can be recycled, and bar sweep speed modified tomatch required dwell times proportional to the fill factor, then theprint speed can be increased such that it is closer to the optimum fillfactor efficiency. In such cases the capital equipment may be fullyutilized. The ability to print with a swept bar of light enablesunidirectional printing, thereby simplifying the gantry system requiredto move the light around. Such ability also allows for easy integrationof the powder sweeping mechanism.

A further example implementation of the print bar concept includes apowder distribution system that follows the bar, laying down the nextlayer of powder as the previous layer is printed. Advantageously, thismay minimize system down time.

Another example implementation of light recycling is to share light withone or more other print chambers. This example effectively makes theavailable laser light seem like an on-demand resource, much likeelectricity being available at a wall outlet.

FIG. 4 illustrates a layout of an example apparatus 400 for laser lightrecycling in the additive manufacturing process. Apparatus 400 mayinclude one or more light sources such as, for example and withoutlimitation, light sources 1, 2, and 3. In some embodiments, lightsources 1, 2, and 3 may include lasers. Alternatively, other types oflight sources such as solid state lasers may be utilized. In someembodiments, each or at least one of light sources 1, 2, and 3 may emit11.1 kW of p-polarized light at 700 nm, having a size of 7.9 cm×7.9 cm,and 7.6 mrad in divergence. Beams of light emitted by light sources 1,2, and 3 may be multiplexed together by a first optical assembly 4,which may include a series of mirrors, thus allowing the beams to be asclose together as possible. These beams are then reshaped and blended byan optical device 5, resulting in a beam 6, 33.3 kW, 4.7 cm×4.7 cm and70.4 mrad in divergence. Beam 6 may then be incident on a spatialpolarization valve 7, that applies a spatial polarization pattern map onbeam 6 by rotating the polarization of selected pixels fromp-polarization to s-polarization to provide a beam 8. With suitablemodifications, the selected pixels can be formed by rotating froms-polarization to p-polarization to provide the beam. In still otherembodiments, grey scale pixels can be created by partial rotations.Transmission losses between light sources 1, 2, and 3 and beam 8 may begiven by Equation 1 and denoted as f₁. Upon interaction with a polarizer9 the s-polarization state of beam 8 may be reflected into a beam 10.The exact fraction may be given by the fraction of light that ispatterned by a spatial polarization valve 7 which is given in Equation 1and denoted as f_(p). Beam 10 may enter a second optical assembly 11,which may include a series of mirrors, re-shaping lenses, waveplates, orother optical components, and may be modified into a 7.9 cm×7.9 cm beamand then re-introduced to the system as if it were a light source 12,along with the original one or more light sources 1, 2, and 3, withlosses given by Equation 1 and denoted as f₂. Power in the finaltransmitted beam 13 may be given by Equation 1 where P₀ is the initialtotal beam power from light sources 1, 2, and 3. With f₁=88.89%,f₂=99.25%, and f_(p)=40%, total transmitted power is 28.3 kW or 85% ofthe total emitted power from the light sources. On the other hand,without recycling, transmitted power would be 60% ignoring losses fromf₁. This results in an effective increase in intensity of 2.12 times,with lasers as the light sources.

In some embodiments, the one or more light sources 1, 2, and 3 mayinclude at least a solid state (e.g. fiber) laser, at least asemiconductor (e.g. diode) laser, or any combination thereof.

In some embodiments, spatial polarization valve 7 may include anoptically addressed light valve or a liquid crystal display device.

In some embodiments, spatial polarization valve 7 may be configured torotate a polarization of one or more pixels from p-polarization tos-polarization to provide the second beam of light. In some embodiments,polarizer 9 may be configured to reflect an s-polarization state of beam8 as beam 10.

FIG. 5 illustrates Equation 1 plotted as the percent of maximum powerdelivered relative to the final transmitted beam 13 as a function of theamount of light rejected due to the applied polarization pattern f_(p)where f₁=88.89%, and f₂=99.25%.

FIG. 6 illustrates Equation 1 plotted as the intensity increase usinglight recycling over the final transmitted beam 13 as a function of theamount of light rejected due to the applied polarization pattern f_(p)where f₁=88.89%, and f₂=99.25%.

FIG. 7 illustrates an example process 700 in accordance with the presentdisclosure. Process 700 may be utilized to realize recycling and reuseof unwanted or otherwise rejected light in additive manufacturing inaccordance with the present disclosure. Process 700 may include one ormore operations, actions, or functions shown as blocks such as 710, 720,730, 740, 750 and 760. Although illustrated as discrete blocks, variousblocks of process 700 may be divided into additional blocks, combinedinto fewer blocks, or eliminated, depending on the desiredimplementation, and may be performed or otherwise carried out in anorder different from that shown in FIG. 7. Process 700 may beimplemented by apparatus 400 and any other suitable laser-based powderbed fusion additive manufacturing system. For illustrative purposes andwithout limiting the scope of process 700, the following description ofprocess 700 is provided in the context of apparatus 400. Process 700 maybegin with block 710.

At 710, process 700 may involve first optical assembly 4 of apparatus400 multiplexing multiple beams of light including at least one or morebeams of light from one or more light sources 1, 2, and 3. Process 700may proceed from 710 to 720.

At 720, process 700 may involve optical device 5 of apparatus 400reshaping and blending the multiple beams of light to provide a firstbeam of light (e.g., beam 6). Process 700 may proceed from 720 to 730.

At 730, process 700 may involve spatial polarization valve 7 ofapparatus 400 applying a spatial polarization pattern on the first beamof light to provide a second beam of light (e.g., beam 8). Process 700may proceed from 730 to 740.

At 740, process 700 may involve polarizer 9 of apparatus 400 splittingpolarization states of the second beam of light 8 to reflect a thirdbeam of light (e.g., beam 10). Process 700 may proceed from 740 to 750.

At 750, process 700 may involve second optical assembly 11 of apparatus400 reshaping the third beam of light into a fourth beam of light.Process 700 may proceed from 750 to 860.

At 760, process 700 may involve second optical assembly 11 of apparatus400 introducing the fourth beam of light to first optical assembly 4 asone of the multiple beams of light to result in a fifth beam of light(e.g., beam 13) that is emitted through and not reflected by polarizer9.

In some embodiments, in receiving the multiple beams of light includingat least one or more beams of light from the one or more light sources,process 700 may involve first optical assembly 4 receiving at least theone or more beams of light from at least a solid state laser or asemiconductor laser.

In some embodiments, in applying the spatial polarization pattern on thefirst beam of light, process 700 may involve applying the spatialpolarization pattern on the first beam of light by spatial polarizationvalve 7 as an optically addressed light valve or a liquid crystaldisplay device.

In some embodiments, spatial polarization valve 7 may be configured torotate a polarization of one or more pixels from p-polarization tos-polarization to provide the second beam of light.

In some embodiments, an amount of power in the fifth beam of light(e.g., beam 13) may be expressed by an equation as follows:

$P = {P_{0}{\frac{\left( {f_{1}f_{p}} \right)}{1 - {f_{1}{f_{2}\left( {1 - f_{p}} \right)}}}.}}$Here, P denotes the amount of power in the fifth beam of light; P₀denotes an amount of power in the one or more beams of light emitted bythe one or more light sources; f₁ denotes an optical transmissionfraction between the one or more light sources 1, 2, and 3 and spatialpolarization valve 7 (in the direction from the one or more lightsources 1, 2, and 3 to spatial polarization valve 7); f₂ denotes anoptical transmission fraction between spatial polarization valve 7 andthe one or more light sources (in the direction from spatialpolarization valve 7 to the one or more light sources 1, 2, and 3); andf_(p) denotes a fraction of the first beam of light (e.g., beam 6) thatis patterned by spatial polarization valve 7.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims. It is also understood that other embodiments of this inventionmay be practiced in the absence of an element/step not specificallydisclosed herein.

The invention claimed is:
 1. An apparatus, comprising: one or more light sources configured to emit one or more beams of light; a first optical assembly configured to receive multiple beams of light including at least the one or more beams of light from the one or more light sources, the first optical assembly further configured to multiplex the multiple beams of light; an optical device configured to reshape and blend the multiple beams of light to provide a first beam of light; a spatial polarization valve configured to apply a spatial polarization pattern on the first beam of light to provide a second beam of light; a polarizer configured to split polarization states of the second beam of light to reflect a third beam of light; and a second optical assembly configured to reshape the third beam of light into a fourth beam of light, the second optical assembly further configured to introduce the fourth beam of light directly to the first optical assembly, in a direction along a direction of the one or more beams of light emitted by the one or more light sources, as one of the multiple beams of light received and multiplexed by the first optical assembly to result in a fifth beam of light of which portions are transmitted through and not reflected by the polarizer.
 2. The apparatus of claim 1, wherein the one or more light sources comprise at least a solid state laser.
 3. The apparatus of claim 1, wherein the one or more light sources comprise at least a semiconductor laser.
 4. The apparatus of claim 1, wherein the spatial polarization valve comprises an optically addressed light valve.
 5. The apparatus of claim 1, wherein the spatial polarization valve comprises a liquid crystal display device.
 6. The apparatus of claim 1, wherein the spatial polarization valve is configured to rotate the polarization state of one or more pixels.
 7. The apparatus of claim 6, wherein the polarizer is configured to reflect one polarization state of the light of the second beam of light as the third beam of light and transmit the second polarization state.
 8. An additive manufacturing apparatus, comprising: a first optical assembly configured to receive multiple beams of light including at least the one or more beams of light from the one or more light sources, the first optical assembly further configured to multiplex the multiple beams of light; an optical device configured to reshape and blend the multiple beams of light to provide a first beam of light; a spatial polarization valve configured to apply a spatial polarization pattern on the first beam of light to provide a second beam of light directable toward a powder bed; a polarizer configured to split polarization states of the second beam of light to reflect a third beam of light; and a second optical assembly configured to reshape the third beam of light into a fourth beam of light, rotate its polarization state to that of the first beam of light, the second optical assembly further configured to introduce the fourth beam of light directly to the first optical assembly, in a direction along a direction of the one or more beams of light emitted by the one or more light sources, as one of the multiple beams of light received and multiplexed by the first optical assembly to result in a fifth beam of light that is transmitted through and not reflected by the polarizer.
 9. The apparatus of claim 8, wherein the one or more light sources comprise at least a solid state laser or a semiconductor laser.
 10. The apparatus of claim 8, wherein the spatial polarization valve comprises an optically addressed light valve or a liquid crystal display device.
 11. The apparatus of claim 8, wherein the energy source is configured to provide the one or more incident beams to bond the powered materials by melting, sintering, alloying, or fusing of the powdered materials, or a combination thereof, to form one or more integral objects, and wherein the powdered materials comprise metallic, ceramic, and polymeric powders suitable for additive manufacturing.
 12. The apparatus of claim 8, wherein the spatial polarization valve is configured to rotate the polarization state of one or more pixels.
 13. The apparatus of claim 12, wherein the polarizer is configured to reflect an s-polarization state of the second beam of light as the third beam of light. 